Indian Journal of Fibre & Textile Research Vol. 24, June 1999, pp, 8 I-85 Air-jet texturing of filament feed yarns of different shrinkage potential V K Kothari & V K Yadav Department of Textile Technology, Indian Institute of Technology, Hauz Khas, New Delhi I IO 016, India Received 10 February 1998; revised received and accepted 23 April 1998 The possibility of feeding filament yarns with different shrinkage potential in air-jet texturing has been studied, Paral- lel-end air-jet texturing of tilament yarns with different shrinkage potential results in decrease of bulk with the increase in shrinkage difference level initially, but then increases with further increase in shrinkage difference, Instability of air-jet tex- tured yarns also tlrst decreases and then increases with the increasing shrinkage difference. The study suggests that shrink- age dilference in the feeder yarn is not an effective"way to increase the bulk of air-jet textured yarns. Keywords: Air-jet texturing, Filament feed'yarn, Shrinkage potential, Textured yarn 1 Introduction Techniques of using differential shrinkage for pro- ducing bulk in the final yam and fabric had been used by several researchers and some of these techniques were exploited commercially. High bulk acrylic yam could be cited as one of the examples. Use of differ- ent shrinkage yams in air-jet texturing has been tried It, a few workers'-J. Piller" 2 used parallel-end air-jet texturing of different shrinkage potential yams and reported higher loop frequency, greater cover, and warm and full hand in the resultant yams after shrink- age. Piller 2 ,4 has also reported that it is not only the shrinka.ge value of feed yarns which decides the shrinkage properties of resultant textured yams but also the shrinkage force and the shrinkage work. He produced different shrinkage in the modified yams by varying draw ratio and drawing temperature and ob- "tained a direct relationship between physical bulk and shrinkage force multiplied by the amount of shrink- age. In the present work, a very low shrinkage yam has been combined with high shrinkage yams pro- duced by changing the hot-pin temperature alone to study the effect of difference in yarn shrinkage on the resultant air-jet yarn properties. 2 Materials and Methods 2.1 Materials Two semi-dull partially-oriented polyester yams of circular cross-section of 125/100 and 126/34 deniers were used for the study. Draw ratios used were 1.564 and 1.632, resulting in yam deniers of 80/100 and 80/34 respectively. Different shrinkage level yarns for each POY '(partially-oriented yam) were produced by varying the hot-pin temperature on the Eltex AT/HS air texturing machine. Hot-pin tem- perature was varied from 60 0 e to 140 0 e in steps of 20 0 e to produce 5 yams of different shrinkage levels. A low shrinkage yam was produced by drawing POY at 140 0 e hot-pin temperature and post heat-stabilizing it at 200 0 e and 15% overfeed. Parallel-end air-jet textured yarns were produced on Eltex AT/HS air texturing machine. Low shrink- age yarn was fed directly to the texturing zone feed roller, whereas the POY was fed to drawing feed roller where it was drawn at different hot-pin tem- peratures to induce different shrinkage potential in one of the ends of the two ends fed to the jet. Tex- tured yarns were then post heat-stabilized sequen- tially on the machine. All textured yams were heat- stabilized at constant tension. Following air-jet tex- turing parameters were kept at constant level: Overfeed to the air-jet ; 25% Texturing nozzle type ; HemaJet with T310 core' Water application ; I litre/h at I bar water pressure Winding underfeed : 0.7 % Air pressure :9 bar Mechanical stretch :4.7% Stabilizing temperature : 200°C Winding tension :4cN Winding speed : 300 mlmin In case of both POYs, an assembled yarn package having low shrinkage and drawn yarn was also pro- duced for measurement of bulk and % increase in lin- ear density and is referred to as the parent yam sam- ple.